A jungle Machete.....takes care of competition fast! Or, something like Captain Jack Sparrow carries. (jk) Which ever knife you pick, stainless is a must (especially around salt water), and it should have an "eye" or loop which you can tie a safety lanyard to. Try putting some Teflon grease on the hinge areas.

Who brings a knife out sailing? I bring my M-4 Carbine with a 30-round clip and CCO. Havn't had to use it yet, but it hooks nicely onto my lifevest...

Remember the rules of combat: Use the proper tool for every job. Sure, long range assault weaponry will work wonders in ship to ship combat, but when you get boarded and there's only a meter between you and your enemy, it requires a more up close and personal weapon. Take Rick's jungle machete as a prime example of how this is supposed to be done... (<--^ jk)

assult rifles are just as effective at 1 yard as 100 yards. But previously i carried a small "sailors rigging knife" with a knife a marlin spike, and shackel key. But it feels cheaply made and i don't need my main knife dying on me on the water

Heres a thought... I was thinking about buying a cheap knife and just lashing it to the line in the middle the tramp, on the bottom of the boat. That way, it's there if I ever needed it. Lash it on, and forget about it. Actually, you could probably access it from either side (top or bottom).

Maybe lash another one around the lower part of the mast. You can buy fairly cheap stainless knifes. A few added ounces will be worth it if the time ever arises that you need it.

BTW, I could get a bayonet for my M4. Then I could cut through lines or shoot through them... just a thought..... ya im just kidding...